Teeter totters or other forms of playground equipment that moves (other than swings) have special safety zone requirements, basically making sure the 6' distance cannot overlap another piece of equipment's 6' safety zone, to avoid collisions due to movement. This doesn't apply to stationary equipment, which can be located 6' from one another with their safety zones overlapping. There is also a lot of motion equipment that is considered unsafe and banned for playgrounds, due to the rate & nature of injuries and/or deaths caused by use of them.
Teeter totters (or the longer seesaws), at their most basic description involves a plank balanced on a central pivot point, often a horizontal pipe, with seats and handles at either end. Ideally, when children of like size and weight sit on the seats at opposing ends, they should balance each other out. When one child kicks off the ground, they shoot upward, sending the child at the other end toward the ground, so they can repeat the same process, back and forth, over and over. Remember there is a direct correlation between the length of the plank and the height of the pivot point, to the maximum height for the seats.
Teeter totters today incorporate safety features like seats with handles placed closely together, both of which make it more difficult to jump onto or slide off safely, or allow more than person to do so, sending the person at the other end shooting upward or dropping more quickly. The same is true for children of different weights and sizes, and all should have adult supervision while being used. A seesaw could be a DIY project with a simple plank of wood, often balanced on a high pipe, reaching maximum seat heights of 5' to 6' or more, and kids could quite literally be catapulted from them. Two more more children jumping off something higher than the raised seat, or someone or something of far greater weight than the child seated on the ground at the other end, dropping suddenly on the raised end does it. They're not safe, yet they used to be considered great fun, and they're not allowed anymore on public playgrounds like that.
Teeter totters and seesaws used to be very popular and resulted in lots of playground injuries, mostly kids impacting their faces or heads, and over the years there are fewer of them being installed in modern playgrounds. Generally, they are still safe, and the limiting factor of a lower pivot point helps to mitigate children going airporne on them. Once again, kids are kids, and they're going to do whatever they dream up, using playground equipment such as teeter totters in unintended ways that can result in falls. Even though there shouldn't be a kid trying to balance themselves above the pivot point, they still do, and can fall hard when they impact the plank or pivot pipe.